Welfare Implications of Tail Docking of Lambs

Literature Review

July 15, 2014
This peer-reviewed summary has been prepared by the American Veterinary Medical Association Animal Welfare Division. While principally a review of the scientific literature, it may also include information gleaned from proprietary data, legislative and regulatory review, market conditions, and scholarly ethical assessments. It is provided as information and its contents should not be construed as official AVMA policy. Mention of trade names, products, commercial practices or organizations does not imply endorsement by the American Veterinary Medical Association.

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The issue

The tail of lambs is shortened, typically using a constricting rubber band, docking iron (hot blade)1 or a combination of the rubber band and a bloodless castrator,2,3 to reduce fecal soiling1 and fly strike.4   Fly strike is a painful condition caused by blowflies that lay their eggs on the sheep.  The maggots then burrow into the flesh and poison the sheep with the ammonia they secrete. As the sheep’s skin becomes irritated, additional flies are attracted to the site.  A sheep can die within three to six days of onset of fly strike.5   Though tail docking has not been shown to consistently improve growth rate, studies have shown that tail docking can increase feed efficiency, reproductive capacity, live weight gain, and heat stress tolerance.6
 

Welfare concerns

Tail docking induces considerable discomfort in young lambs.5 Short docking of the tails of lambs has also been linked to increased incidence of rectal prolapse.
 
Short docks—Docking of the tails of show animals may sometimes involve amputation of the entire tail to give a fuller appearance to the rump (short docking).
 
Three large studies tracked the incidence of prolapse in lambs whose tails were docked at different lengths. Those whose tails were docked at the end of the caudal fold had a significantly lower incidence of prolapse than those whose tails were short docked, but the effect was small, partly due to a low overall incidence of prolapse (1% vs. 6%, rd=.05 z=6.1, p<.0001).8,9,10
 
Other factors have also been implicated in the incidence of prolapse including raising in feedlots11, coughing, and sex (females at higher risk).12,13  The appearance of short docks increasing risk of prolapse may be a result of  these confounding variables.8,9,14,15   Nevertheless, a minimum length of tail to qualify for showing has been proposed11 and implemented in some states. The appropriate length for docking is variously expressed as visibility  of 0.7 inches of tail, docking at the third or fourth coccygeal vertebrae, or docking at the end of the caudal fold/hairless under-tail area.
 
 

Pain—Active behavioral responses indicating pain are restlessness, rolling, easing quarters (the hind quarters are moved slowly and alternately without locomotion), stamping, kicking, head turning and vocalization by the lamb.2,3,11 High concentrations of cortisol in the blood are also associated with pain and distress.2,3,16   Increased active behavior, as well as elevated peak blood cortisol concentrations are seen in lambs undergoing tail docking.2,3,12

Techniques

Rubber ring—One technique for docking tails is use of an elastrator to apply a tight latex band (rubber ring docking).  The use of latex bands produces highly variable responses, not only among lambs, but within the same animal if the band is removed and then replaced.  Rubber ring docking produces highly variable levels of pain within the first hour after application.5,12,17 Pain is typically estimated to be mild18  or moderate based on abnormal postures and behaviors indicating discomfort.12,13 This suggests that some band placements are more painful than others.  For example positioning a band on the vertebra might be expected to be more painful than positioning one over an intervertebral space.5   Cortisol concentrations in blood may also be elevated.12 The ring subsequently produces an inflammatory lesion and sloughing of the tail (most slough by 28 days after rubber ring placement15), which may be associated with a longer term pain response.  Docking with a rubber ring, however, does not typically affect live weight gain.19   
 

Hot blade—The hot blade method involves severing the tail and cauterizing it, using a heated anvil scissor docking iron.  The cut end of the tail is held against the heated blade for approximately 1 second to improve hemostatis.3 Tail docking performed with a heated docking iron has been shown to produce levels of pain behavior and blood cortisol concentrations that are not significantly different from handled lambs whose tails are not docked.3

Rubber ring followed by crushing—A rubber ring may also be applied as described above followed by application of a bloodless castrator across the full width of the tail for approximately 10 seconds.2,3 The rubber ring generally rolls into the groove made by the bloodless castrator.2  It has been shown that the application of a bloodless castrator in addition to rubber ring placement did reduce active behavioral pain responses (see section on pain above) and increases in blood cortisol concentrations associated with docking.2 

Analgesia

Oral aspirin was not found to be an effective analgesic when administered immediately after application of rubber rings.13 Another study found that neither suckled sucrose nor administration of carprofen altered behaviors indicating discomfort (e.g. restlessness, vocalization, tail wagging, etc.) associated with rubber ring tail docking.20   One research group found that 2% lignocaine applied locally reduced peak blood cortisol concentrations and behavioral pain responses (see pain section above) to tail docking with a rubber ring.2   Bupivacaine administered subcutaneously immediately before rubber ring application has also been effective in reducing active painful behavior and peak blood cortisol concentrations.3
 

Alternatives

Genes associated with short tails exist in sheep and offer a potential alternative to docking, via selective breeding toward a tail of the desired length.21  Fly strike might also be managed in some cases by removal of fleece (i.e. crutching) and increased application of chemical preventatives (i.e. jetting).  However the use of a slow release capsule of a benzamidizole (albendazole) was not found to be as effective as docking in preventing flystrike.1
 

Summary

Fly strike is a cause of serious suffering in lambs.  Subjective monitoring of behavioral responses and objective monitoring of cortisol concentrations in blood indicate there is pain and distress associated with tail docking, no matter the technique used.  Short-docked tails have been associated with increased incidence of rectal prolapse in some studies.  Though there is pain associated with tail docking, fly strike can lead to discomfort, pain and eventually death of the lamb.
 
The Farm Animal Welfare Council (FAWC) recommends that docking should be avoided whenever possible.22 The FAWC also concluded that tail docking of lambs up to 7 days old is best done with a rubber ring; that lambs between the ages of 1 and 8 weeks old should be docked with a docking iron (hot blade) or a clamp; and that acute pain of tail docking can be alleviated using locally applied anesthetics.18 

REFERENCES
1 Webb Ware JK, Vizard AL and Lean GR. Effects of tail amputation and treatment with an albendazole controlled-release capsule on the health and productivity of prime lambs.  Aust Vet J. 2000;78:838-842.
2 Kent JE, Molony V and Graham MJ. Comparison of methods for the reduction of acute pain produced by rubber ring castration or tail docking of week-old lambs. Vet J. 1998;155:39-51.
3 Graham MJ, Kent JE, and Molony V. Effects of four analgesic treatments on the behavioural and cortisol responses of 3-week-old lambs to tail docking. Vet J. 1997;153:87-97.
4 Guatteo R, Guemene D. Sources of known and/or potential pain in farm animals. Advances in Animal Biosciences 2014;5:319-332.
5 Morris MC. Ethical issues associated with sheep fly strik research, prevention, and control. J Ag Envir Ethics. 2000;13:205-217.
6 Alkass JE, Darwesh KA, Merkhan KY. Performance of docked vs. undocked fat-tailed sheep: A review. Advanced Journal of Agricultural Research 2014;2:29-37.
7 Graham MJ, Kent JE and Molony V. The influence of the site of application on the behavioural response of lambs to tail docking by rubber ring. Vet J 2002;164:240-243.
8 Windels, H. 1990. Factors causing rectal prolapse in feedlot lambs. Pages 10–13 in Proc. 62nd Annual Sheep and Lamb Feeders Day, Univ. of Minnesota, Morris.
9 Zanolini, William F. "The effects of dock length on the incidence of rectal prolapse in lambs." PhD diss., Texas Tech University, 2006.
10 Thomas, D. L., D. F. Waldron, G. D. Lowe, D. G. Morrical, H. H. Meyer, R. A. High, Y. M. Berger et al. "Length of docked tail and the incidence of rectal prolapse in lambs." Journal of animal science 81, no. 11 (2003): 2725-2732.
11 Anderson DE and Miesner MD. Rectal prolapse. Veterinary Clinics of North America: Food Animal Practice 2008; 24: 403-408.
12 Luther J. Causes, prevention and treatment of rectal prolapse in sheep. NDSU Extension Services September 2008. AS-1388.
13 Thomas DL, Waldron DF, Lowe GD, Morrical DG, Meyer HH, High RA, Berger YM, Clevenger DD, Fogle GE, Gottfredson RG, Loerch SC, McClure KE, Willingham TD, Zartman DL and Zelinsky RD . Length of docked tail and the incidence of rectal prolapse in lambs. J Anim Sci 2003;81:2725-2732.
14 Windels H. Factors causing rectal prolapse in feedlot lambs. Proceeding 62nd annual sheep and lamb feeders day, University of Minnesota. 1990;10-13.
15 Goodwin J, Murphy T and Jacobson R. A path to resolution regarding the show lamb taildocking controversy. J Extension 2007;45:Article 4FEA8.
16 Molony V, Kent JE and McKendrick IJ. Validation of a method for assessment of an acute pain in lambs. Appl Anim Behav Sci 2002;76:215-238.
17 Pollard JC, Roos V and Littlejohn RP. Effects of oral does of acetyl salicate at tail docking on the behavior of lambs aged three to six weeks. Appl Anim Behv Sci 2001;71:29-42.
18 Mellor DJ and Murray L. Effects of tail docking and castration on behaviour and plasma cortisol concentrations in young lambs. Res Vet Sci 1989;46:387-391.
19 Kent JE, Jackson RE, Molony V, and Hosie BD. Effects of acute pain reduction methods on the chronic inflammatory lesions and behavior of lambs castrated and tail docked with rubber rings at less than two days of age. Vet J 2000;160:33-41.
20 Price J and Nolan AM. Analgesia of newborn lambs before castration and tail docking with rubber rings. Vet Rec. 2001;149:321-324.
21 Scobie DR and O-Connell D. Genetic reduction of tail length in New Zealand sheep. Proceedings of the New Zealand Society of Animal Production 2002;62:195-198.
22 Farm Animal Welfare Council. FAWC report on the implications of castration and tail docking for the welfare of lambs. FAWC, London, England. June 2008. Available at: fawc.org.uk/pdf/report-080630.pdf  Accessed February 18, 2010.